Wheelchair users may be active or passive wheelchair users. Active wheelchair users tend to manage the movement of their wheelchair and its assembly and disassembly when required, for example loading and unloading to and from a car, independently. Passive wheelchair users may also be relatively independent but rely upon a third party for movement and/or assembly/disassembly of wheelchair from time to time.
Many wheelchairs are adapted for the comfort of a user having seat bases and seat backs made from material slung between two parallel struts. This may be supplemented by foam filled cushions which both support and provide comfort to a user. Some wheelchair such as wheelchairs designed for sports may have rigid seat bases and seatbacks to provide firm supports that a user push against when using the push rims on wheels to drive the wheelchair forward or when reaching for a ball.
One difficulty faced by wheelchair users is that of transfer from the seat base of the wheelchair to another seat, such as the chair or a car seat. Typically, wheelchairs have two front support struts at the sides of the wheelchair one on either side of a user's legs. These side support struts lead down to a footrest for supporting the feet as well as supporting the seat base on front wheels. These support struts get in the way when trying to transfer from one seat base to another. Thus, the seat base of the wheelchair cannot be brought close to the seat base of another chair or a car seat because the side support struts are in the way.
Many wheelchairs are of box frame construction having a seat base supported at front and rear ends by downwardly supporting members and one or more cross struts extending from the front to the rear between the downwardly supporting members forming a box shape when viewed from the side. Other wheelchair designs are of a cantilever type having a seat base supported at front and rear ends by downwardly supporting members and no cross struts or other structural connection between these downwardly supporting members. Thus, in a cantilever design the seat base provides structural strength between the downwardly depending supporting members and so to the overall frame, whereas in a box frame design the one or more cross struts or other structural connection provide structural strength between the downwardly depending support members and so to the overall frame. A box frame design may in addition be provided with structural strength via the seat base, but this is not always the case. Thus, a seat base made of fabric would not offer any structural benefit, whereas a solid seat base may do so. Further, a box frame will offer a more rigid structure than a cantilever frame and is usually lighter than a cantilever frame. Due to a cantilever frame not having cross struts as seen on a box frame, a cantilever frame will usually need to be constructed from thicker and heavier materials. A cantilever frame made from light weight metals such as titanium will suffer from flexion not seen in the box frame design. The benefit of the cantilever frame is that it is more compact for stowage than the box frame.
Foldable wheelchairs are particularly useful for car users because these can be folded (disassembled) for loading and unloading to and from a vehicle. Nevertheless, folding wheelchairs are not ideal as their rigidity is dependent upon the rigidity of the folding joints and clamps when in use. This is also true for wheelchairs having adjustable components such as adjustable side support struts or adjustable front support struts.
A rigid wheelchair, as opposed to one that is foldable or has movable joints, is more energy efficient as energy is not lost from a user's muscles to the wheelchair in flexing the joints when simply trying to move the wheelchair. Thus, a wheelchair designed to have folding and/or adjustable and/or flexible parts to meet a users sizing and comfort needs can soak up the energy that an active wheelchair user would prefer not to expend on such unproductive energy losses.
Further problems faced by the wheelchair users include those of 1) seeing the ground immediately ahead of the wheelchair when it is dark, 2) degradation of the wheelchair and its ease of rotation following exposure to water such as puddles 3) black marks on hands from wheelchairs constructed of aluminium (other metals also leave metallic residue) that are transferred to the user surroundings and can also be slippy to grip when wet.
U.S. Pat. No. 4,887,826 (KNATNER) describes a lightweight foldable wheelchair having first and second struts hingedly mounted to the underside portion of the seat base of the seat. The forward ends of both struts meet below and forward of the seat and secure a demountable castor wheel and hingedly mounted folding footrests.
U.S. Pat. No. 5,480,172 (JAMES) describes a three wheeled competition wheelchair having an adjustable centre of mass. A footrest assembly has two seat support posts having one end movably mounted to the seat frame and an opposite end carrying footplates which is movingly mounted longitudinally along a frame beam. The frame beam extends from a main wheel crossbar of the wheelchair and terminates at a front wheel.
U.S. Pat. No. 5,480,179 (PEACOCK) describes a collapsible wheelchair having an L-shaped monocoque chassis extending between a main wheel crossbar and a footrest.
GB2427674 (SCARSI) describes a wheelchair armrest pad incorporating a lighting unit having three LEDs in an armrest. AU2005100037 (ZHANG) discloses a wheelchair headlight positioned in a joystick control of a wheelchair. U.S. Pat. No. 6,702,314 (CROSE) describes a wheelchair lighting system having a plurality of light assemblies coupled to the handles of the wheelchair.
U.S. Pat. No. 3,679,257 (JACUZZI) describes a foldable wheelchair. The three wheeled wheelchair has a solid seat back, the back being hinged for folding down upon the seat, while the side wheel and front wheel assemblies are hingedly secured for folding under the seat, the entire wheelchair in its folded condition being of light weight capable of storage in the trunk of a car.
GB2458852 (SMURTHWAITE) shows a manually driven wheelchair of a standard box type construction.
DE4114710 (BEESE) describes a wheelchair with brakes. US20070012526 (HOLUB) describes a wheelchair having inboard disc brakes. GB2448688 (JCM) describes a wheelchair having a segmented seatback assembly. Two adjustable front seat support struts are shown.
X-core wheels available from Spartak Corporation, Indiana USA are made of carbon fibre with welded hard anodised aluminium hand rims. An all terrain wheelchair available from www.trekinetic.co.uk uses a carbon fibre monocoque seat. British company Future Chairs Ltd, UK and Italian firm Progeo of Italy both produce a carbon fibre model of wheelchair. Swedish firm Panthera also produce a carbon fibre box frame wheelchair.
US2005006871 (GODING) describes an ergonomically designed wheelchair wheel having an integral hand push rim. The wheel may be made from carbon fibre. Nevertheless this design of push rim is poorly suited to manufacture by carbon fibre to provide sufficient strength in use. U.S. Pat. No. 4,366,964 (FAREY) describes a wheelchair hand rim having a cross functional contour conFigured to optimise the gripping surface. JP7304302 (HASHIMOTO) describes a hand rim for a wheelchair wheel. JP11347072 (MASANORI) describes a wheelchair wheel having an outer case and a hand part protruding from it. FR2700726 (DAVID) describes the use of carbon fibre in wheelchairs. U.S. Pat. No. 6,241,321 (GAGNON) describes an all-terrain wheel for a wheelchair having an integral push rim.
Wheelchair design has evolved very little over the last twenty five years. One area of development is in wheelchair materials with choices of aluminium, titanium and alloy being popular. Carbon fibre usage is still very small although it is available in a couple of conventionally styled wheelchairs. Aluminium offers a lightweight material choice with good stiffness but comes with compromises. Aluminium frames are very prone to damage from knocks and scrapes. The need for strength means more material is needed; weight saving benefits are then compromised. Aluminium is not a pleasant material to handle leaving black residue on surfaces it contacts including hands. Titanium has excellent strength to weight properties. However, it is not a stiff material and cantilever frames flex considerably. A frame that flexes does not behave predictably and is less energy efficient. Alloy frames offer stiffness and strength but are heavier than the other metals. The strength, weight and stiffness benefits of carbon fibre are not best utilized in traditional tubular design common in wheelchairs. Furthermore, conventional wheelchair designs have two front stems one either side of the users legs.
Typically, wheelchairs are usually constructed from simple tubular frames fitted with size adjustable upholstery. This method of construction offers the manufacturer an easy means of creating bespoke sizes to suit users dimensions. Made to measure has become standard practice in the high end wheelchair industry. This method of construction throughout the industry has lead to all chairs suffering the same design flaws. Many components are generic across brands continuing a circle of faulty design.
To understand the benefits of the design it is important to grasp four basic needs of the active independent wheelchair user. 1) Weight the weight of a wheelchair is the number one priority for the user when choosing a chair. A lightweight chair not only makes for easier pushing by the user, it makes for easier lifting. An independent user will frequently have to collapse and lift their chair in and out of a vehicle. 2) Styling: Users demand a chair that looks good and as much as possible compliments their own style. Independent wheelchair users want to look good and not be seen as users of ugly medical devices. In an exemplary embodiment the wheelchair will use F1 technology and look as good as it performs. 3) Performance: our end user is the kind of individual that knows no boundaries. They will take their chair into every conceivable environment and expect it to perform. The wheelchair is a workhorse and an unavoidable extension of themselves. It should not be unreasonable for a user to want to paddle in the sea, take their chair through sand, mud, snow, over dirt tracks or gravel, through the woods or grass. Energy efficiency and minimal rolling resistance are key qualities a demanding user looks for. The user of exemplary embodiments of wheelchair according to the present invention will be preserving their joints and energy from unnecessarily heavy pushing and lifting in comparison to users of conventional chairs. A good chair will have a rigid frame (not a folding frame) with quick release wheels and a folding backrest. These elements will give a durable compact chair for rough usage and compact stowage. 4) Frame shape: A modern wheelchair will be compact in use and dismantle for easy storage. For storage purposes it is standard that the main wheels are fitted with quick release axles and that the backrest folds flat to rest face down on the seat.
The shape of the frame is itself important. Cantilever designs offer the most compact and versatile shape. The clear space underneath the cantilever compared to the box frame design makes for easy maneuverability when lifting the frame into a car, passing it between user and steering wheel. Although heavier than the box frame, once in the car the cantilever frame takes up less space. An ideal design would offer the rigidity, strength and weight of the box frame with the compactness of the cantilever design.
One problem with the conventional two stem design is that the stems prevent the user getting their body close to surfaces for transfers. This is a particular problem for car transfers. The car door sill contacts the chair and stops the user getting themselves close for easy transferring. The user will have to make a transfer from their wheelchair over the gap between door sill and car seat. Many users will use transfer boards to bridge large gaps. The user will slide along the board from wheelchair to car, bed, toilet etc.
Most light weight wheelchairs weigh around 10 kg when fitted with wheels, tyres, brakes and upholstery. Some chair manufacturers make claims of under 7 kg, but often this is the weight of their smallest size of chair in its minimal configuration.
Conventional backrest designs are made up of two vertical poles fitted with a fabric sling and upholstery between them. After a short amount of time the post tops tear through the upholstery and the sling fabric stretches. The user soon suffers pressure points as the exposed vertical posts dig into their back. Sling upholstery moves when the user pushes forward, therefore a proportion of the users energy is being lost by the absorption of the fabric. A flimsy generic folding mechanism used across most wheelchair brands to fold the backrest often fails and comes loose. The height of conventional sling backrests can be adjusted to suit the user. However, adjusting the height requires the removal of the upholstery and using tools to extend telescopic poles.
A conventional wheelchair uses a telescopic footrest secured at a desired height with a bolt. Adjusting the height with such a design requires tools, and for the user to be out of the wheelchair. This awkward system means that once the footrest is initially set up it is very rarely changed. However, there are circumstances when easy fine adjustment of the footrest would be very useful. Sometimes, a conventional wheelchair has a height adjustable footrest that is independent of the front wheels. Foot position is important to how comfortably the user sits and is fundamental to keeping good balance. When a user wears different shoes or goes bare foot their feet will no longer sit on the footrest in the perfectly correct position. As the initial set up would have been done wearing shoes, going bare foot will mean the users feet are at least 10 mm higher than the footrest 10 mm is enough to cause considerable discomfort and balance problems with the feet not sitting firmly flat on the footrest. Changing from training shoes with thick rubber soles into dress shoes with less grip and a thinner sole can result in feet sliding off the footrest. Other situations such as wet weather, bumpy surfaces and muscle spasms can also cause feet to slip off the footrest.
Using a wheelchair in the dark is a hazardous activity. Unlike an able bodied individual walking across an unpredictable surface, a wheelchair user can't feel the ground under foot. It is not until the small front castors wheels hit an object that the user knows of the hazard, by which time it may be too late. Falls from wheelchairs are often the result of the small front wheels becoming jammed on a stone or pot hole, stopping the chair instantly. The chair will often tip forward and the user fall out the front. It is virtually impossible for a wheelchair user to push their chair and carry a torch at the same time. Moving safely in the dark is a very difficult, slow and precarious exercise.
Wheels and push rims account for approx 5 kg of a wheelchairs weight. Conventional wheelchairs use bicycle wheels with modified hubs and bolted on push rims. Push rims are traditionally made from aluminium tubing and are very inefficient for gripping and pushing the chair. A user will commonly grip the tyre rather than the push rim in order to get sufficient grip. In wet weather the aluminium push rims are impossible to grip for slowing and steering the chair. Aluminium push rims also leave the user with scrapes and black residue over their hands and around their home where the push rim has contacted a surface. Doors, door frames, sink pedestals, toilets and white goods etc all get damaged. Wheelchairs cause considerable damage around the home and to the user's car with chipped paint, torn and oil damaged interiors.
Wheelchairs typically have twelve sets of steel sealed bearings, namely 2×2 each main wheel, 2×2 each front wheel, 2×2 each castor housing. Twelve sets of steel bearings add a considerable weight to the wheelchair and cause other difficulties. The reliance on lubricant is a problem for the wheelchair user. A wheelchair should be able to enter any environment the user requires. However, lubricant is easily washed away leaving the user with a squeaking unresponsive chair. Taking a wheelchair through snow and foul weather will strip the oil from the front axles. Even using the shower in a luxury hotel can result in embarrassing squeaky wheels. A user would not normally sit in their wheelchair when in the shower, but they do need to get to the shower and keep their chair near to them to leave again. Most hotels have fold down seats for the guest to use within a wheel in shower. The hot soapy spray that inevitably covers the waiting wheelchair when using this seat strips it of oil around the axles and bearings. When the quick release wheels on conventional wheelchairs are removed for stowing the chair in a car, the oil covered axle is left exposed. The axles leave oil on everything they touch, hands, clothes, car interior etc. Ceramic bearings alone will not remove the need for lubricant on the axles. Although the wheels will rotate on lubricant free ceramic bearings, lubricant will be needed to slide the axle in and out of its port on the chair.
The chair will need the capability of carrying weight while dropping of kerbs, being lifted up steps, usage on uneven ground and various surface materials. Going up and down kerbs is a fundamental need for the independent user. To achieve this, the chair should always go up or down the kerb in a straight line so both wheels encounter the kerb together. However, sometimes it is not possible to operate in a straight line. A user waiting for a ramp to get off a train may be let down and have to drop off a 12″ step on their back wheels. Impacts are also a serious consideration. A user will use the front edge of the footrest to push open heavy doors by simply bashing into them. If the door is locked or is a pull not a push door this can result in a hard impact. As far as wheels are concerned we have similar issues to consider. A user will bunny hop their chair to get around tight corners, roll up and down kerbs and turn 360 on soft surfaces putting a twisting strain on the wheel. Simple variations in tyre pressure will cause very different stresses when turning 360.
Wheelchairs users in the high end market demand made to measure chairs that fit their proportions and are set up for their specific needs. One wheelchair size will not fit all users, therefore to avoid introducing adjustable mechanisms that reduce rigidity and add weight, the invention seeks to provide a method of manufacturing to address this. Seat width, seat depth and leg length are the key measurements that must be tailored to individual user needs. Exemplary embodiments of the present invention may achieve multiple sizes and configurations without producing individual tooling for each customer, or producing a generic size adjustable wheelchair that will be heavy.
Standard wheelchair brakes operate on a leverage system that presses against the tyres of the main wheels. The problem with these brakes is that they are dependent on tyre pressure and wheel position to operate effectively. Therefore, the brake itself must be position adjustable along the edge of the seat to find the perfect leverage. Even when the perfect position is found it will not be long before the tyre deflates a little and the brake no longer works. It is a common injury for users to trap their thumbs between the moving wheel and braking arm lever when pushing the chair. A further common injury is trapping thumbs or fingers between the moving wheel and moving push rim.
The present invention and its several aspect seeks to alleviate one or more of the problems outlined above.